A method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate

Abstract

The application discloses a method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate. The method for preparing phosphoric acid is to use phosphate rock and ammonium sulfate as raw materials and adopt high-temperature solid-state reaction to prepare pure phosphoric acid. Compared with a traditional process, the whole process flow is simple and convenient to operate. Compared with other thermal methods, the energy consumption of the method is lower, the recycling of ammonium sulfate is realized, the process cost is reduced to a certain extent, and the utilization and conversion of medium and low grade phosphate rock are realized.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate, and belongs to the chemical industry field. BACKGROUND

[0002] As a main chemical raw material of phosphorus elements, phosphate rock is an important non-metallic mineral resource and an indispensable raw material for the development of national economy, and is mainly used for manufacturing phosphate fertilizer, yellow phosphorus, phosphate, phosphate-containing compound fertilizer and other various phosphorus-containing additives and dyeing agents and other phosphorus products, and is widely applied in the fields of chemical industry, agriculture, light industry, metallurgical industry, ceramics, national defense department and the like, and is one of indispensable materials for the development of high technology at present, and plays an important role in the rapid development of national economy of China.

[0003] At present, the total amount of phosphate rock resources in China ranks the second in the world, and China is a large country of phosphate rock resource reserves. However, due to the uneven distribution of phosphate rock resources, the south is more than the north, and the overall development trend is relatively single. In the phosphate rock resources in China, the amount of high-grade phosphate rock is small, and most of the phosphate rock is of medium and low grade, and the mining difficulty is high, the cost is high, and the impurities are many, so it is difficult to meet the needs of production enterprises. Moreover, improper exploitation and utilization will cause excessive accumulation and cause environmental pollution and other problems, which seriously hinders the development of the phosphate rock industry and the country. Therefore, continuously improving and developing the utilization rate of phosphate rock resources is the main direction of the current development.

[0004] The technologies for pretreating medium and low grade phosphate rock in China include flotation, ore washing, gravity separation, calcination, acid method, microbial dissolution of phosphorus and the like. At present, there are two kinds of most commonly used methods for producing phosphoric acid: wet-process phosphoric acid and thermal-process phosphoric acid. The wet-process phosphoric acid method is to decompose phosphate rock by using inorganic acid (such as sulfuric acid, hydrochloric acid, nitric acid and the like) to obtain phosphoric acid, and this process has low cost and low energy consumption, but the grade requirement of phosphate rock is high, and the concentration of prepared acid is low, and the process flow is relatively complex. Compared with the wet-process phosphoric acid, the thermal-process phosphoric acid has high purity and a relatively simple process flow, but the energy consumption and process cost are relatively high.

[0005] Through the analysis and thinking of the wet-process phosphoric acid and the thermal-process phosphoric acid, the application adopts the high-temperature solid-state reaction of the reactants phosphate rock and ammonium sulfate, and the two are fully reacted under the condition of high temperature through stirring, so that the conversion process of medium and low grade phosphate rock to phosphoric acid is achieved. The whole process flow is simple and convenient to operate, and the energy consumption is relatively low compared with other thermal-process phosphate rock, and the recycling of ammonium sulfate is realized, the process cost is reduced to a certain extent, and the utilization and conversion of medium and low grade phosphate rock are realized. SUMMARY

[0006] The application aims to provide a method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate.

[0007] The technical solutions of the present application The application aims to provide a method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate.

[0008] The specific steps of the foregoing method are as follows:

[0009] (1) The phosphate rock and ammonium sulfate are weighed respectively and placed in an evaporating dish, and high-temperature heating reaction is performed using an electric heating jacket. The stirring is continuously performed during the heating process, and the crude phosphoric acid is obtained after the reaction is completely cooled.

[0010] (2) The crude phosphoric acid is taken and extracted by adding methanol. The extraction process is fully stirred, and the vacuum pump filter is used for filtration to obtain the phosphoric acid filtrate and the filter residue.

[0011] (3) The phosphoric acid filtrate is taken and distilled by using a rotary evaporator to obtain pure phosphoric acid.

[0012] (4) The filter residue is dissolved by adding water, and the vacuum pump filter is used for filtration. The filtrate is taken, and the impurity residue is removed. The filtrate is an ammonium sulfate solution, which can be used for the cyclic preparation of phosphoric acid.

[0013] In the foregoing step (1), the mass ratio of the phosphate rock to the ammonium sulfate is 1:1-6.

[0014] Specifically, in the foregoing step (1), the mass ratio of the phosphate rock to the ammonium sulfate is 1:3.

[0015] In the foregoing step (1), the temperature of the high-temperature heating reaction is 250-300°C, and the reaction time is 30-40 min.

[0016] Specifically, in the foregoing step (1), the temperature of the high-temperature heating reaction is 270°C, and the reaction time is 30 min.

[0017] In the foregoing step (2), the addition amount of the methanol is 100-150 g, and the extraction time is 10-60 min.

[0018] Specifically, in the foregoing step (2), the addition amount of the methanol is 120 g, and the extraction time is 20-60 min.

[0019] In the foregoing step (3), the distillation temperature is 60-100°C, the rotation speed is 50-70 r / min, and the distillation time is 30-100 min.

[0020] Specifically, in the aforementioned step (3), the distillation temperature is 80℃, the rotation speed is 60r / min, and the distillation time is 40-90min.

[0021] The beneficial effects of the present application

[0022] 1. The present application adopts mixing of reactants phosphate rock and ammonium sulfate for high-temperature solid-state reaction, and fully reacts them under high-temperature conditions through stirring, so as to achieve the conversion process of low-grade phosphate rock to phosphoric acid. The whole process is simple and easy to operate, and has lower energy consumption compared with other thermal methods of phosphate rock, which reduces the process cost to a certain extent, realizes the utilization and conversion of low-grade phosphate rock.

[0023] 2. The recycling of ammonium sulfate is realized, and the unreacted ammonium sulfate in the filter residue after the reaction is also separated. The filter residue separated is calcium sulfate and other impurity filter residues, and the filtrate after separation is ammonium sulfate solution, which can be used for high-temperature solid-state reaction with phosphate rock again, saving resources. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 : Process flow diagram for preparing phosphoric acid by ammonium sulfate method for decomposing phosphate rock;

[0025] Figure 2 : Effect of reaction temperature on phosphoric acid yield;

[0026] Figure 3 : Effect of the ratio of ammonium sulfate to phosphate rock on phosphoric acid (P2O5) yield;

[0027] Figure 4 : Effect of reaction time on phosphoric acid yield. DETAILED DESCRIPTION

[0028] The present application will be further described below in combination with examples, but it is not used as the basis for limiting the present application.

[0029] Embodiments of the present application

[0030] Example 1

[0031] (1) 5g of phosphate rock and 15g of ammonium sulfate were respectively weighed and placed in an evaporating dish, and high-temperature heating at 270℃ was carried out using an electric heating jacket for 30min, and continuous stirring was carried out during the heating process. After the reaction was completely cooled, a crude phosphoric acid was obtained. The crude phosphoric acid was taken and 120g of methanol was added for extraction, and the extraction process was carried out for 40min with sufficient stirring, and a vacuum pump filter was used for filtration to obtain phosphoric acid filtrate and filter residue; the phosphoric acid filtrate was taken and distilled at 80℃ using a rotary evaporator, the rotation speed was 60r / min, and the distillation time was 60min, and pure phosphoric acid was obtained.

[0032] (2) The filter residue is dissolved in water, vacuum pump filter is used for filtration, the filtrate is taken, the impurity filter residue is removed, the filtrate is ammonium sulfate solution, which can be used for the cyclic preparation of phosphoric acid.

[0033] Example 2

[0034] (1) 5g of phosphate rock and 30g of ammonium sulfate are weighed respectively and placed in an evaporating dish, high-temperature heating at 300 DEG C is carried out using an electric heating jacket for 40 min, continuous stirring is carried out during the heating process, after the reaction is completely cooled, a crude phosphoric acid product is obtained, the crude phosphoric acid product is taken and 150g of methanol is added for extraction, sufficient stirring is carried out for 60 min during the extraction process, and vacuum pump filter is used for filtration, phosphoric acid filtrate and filter residue are obtained; the phosphoric acid filtrate is taken and distilled using a rotary evaporator at a temperature of 100 DEG C, the rotation speed is 70 r / min, and the distillation time is 100 min, pure phosphoric acid is obtained;

[0035] (2) The filter residue is dissolved in water, vacuum pump filter is used for filtration, the filtrate is taken, the impurity filter residue is removed, the filtrate is ammonium sulfate solution, which can be used for the cyclic preparation of phosphoric acid.

[0036] Example 3

[0037] (1) 5g of phosphate rock and 30g of ammonium sulfate are weighed respectively and placed in an evaporating dish, high-temperature heating at 300 DEG C is carried out using an electric heating jacket for 40 min, continuous stirring is carried out during the heating process, after the reaction is completely cooled, a crude phosphoric acid product is obtained, the crude phosphoric acid product is taken and 150g of methanol is added for extraction, sufficient stirring is carried out for 60 min during the extraction process, and vacuum pump filter is used for filtration, phosphoric acid filtrate and filter residue are obtained; the phosphoric acid filtrate is taken and distilled using a rotary evaporator at a temperature of 100 DEG C, the rotation speed is 70 r / min, and the distillation time is 100 min, pure phosphoric acid is obtained;

[0038] (2) The filter residue is dissolved in water, vacuum pump filter is used for filtration, the filtrate is taken, the impurity filter residue is removed, the filtrate is ammonium sulfate solution, which can be used for the cyclic preparation of phosphoric acid.

[0039] Example 4

[0040] (1) 5g of phosphate rock and 30g of ammonium sulfate are weighed respectively and placed in an evaporating dish, high-temperature heating at 300 DEG C is carried out using an electric heating jacket for 40 min, continuous stirring is carried out during the heating process, after the reaction is completely cooled, a crude phosphoric acid product is obtained, the crude phosphoric acid product is taken and 150g of methanol is added for extraction, sufficient stirring is carried out for 60 min during the extraction process, and vacuum pump filter is used for filtration, phosphoric acid filtrate and filter residue are obtained; the phosphoric acid filtrate is taken and distilled using a rotary evaporator at a temperature of 100 DEG C, the rotation speed is 70 r / min, and the distillation time is 100 min, pure phosphoric acid is obtained;

[0041] (2) The filter residue is dissolved with water, vacuum pump filter is used to perform suction filtration, the filtrate is taken, the impurity filter residue is removed, the filtrate is ammonium sulfate solution, and the filtrate can be used for cyclic preparation of phosphoric acid.

[0042] Example 5

[0043] (1) 5 g of phosphate rock and 10 g of ammonium sulfate are respectively taken and placed in an evaporating dish, high-temperature heating of 260 DEG C is performed using an electric heating jacket for 35 min, stirring is continuously performed during the heating process, after the reaction is completely cooled, a crude phosphoric acid product is obtained, the crude phosphoric acid product is taken and 130 g of methanol is added to perform extraction, the extraction process is performed with sufficient stirring for 50 min, and vacuum pump filter is used to perform suction filtration, to obtain phosphoric acid filtrate and filter residue; the phosphoric acid filtrate is taken and distilled using a rotary evaporator at a temperature of 80 DEG C, the rotation speed is 55 r / min, and the distillation time is 70 min, to obtain pure phosphoric acid;

[0044] (2) The filter residue is dissolved with water, vacuum pump filter is used to perform suction filtration, the filtrate is taken, the impurity filter residue is removed, the filtrate is ammonium sulfate solution, and the filtrate can be used for cyclic preparation of phosphoric acid.

[0045] In order to verify the beneficial effects of the present application, the inventors have carried out a large number of experimental researches, and the experimental process and results are as follows:

[0046] 1. Experimental part

[0047] 1.1 Instruments

[0048] Experimental instruments: electronic scale (ELECTRONIC SCALE), electric heating jacket heating device, electronic scale (ELECTRONIC SCALE), water bath, vacuum pump filter (SHB-IIIG), electric heating air drying oven (GFL-125), heat collecting type constant temperature heating magnetic stirrer (RE-2000Z), rotary evaporator (RE-2000A).

[0049] 1.2 Experimental raw materials and reagents

[0050] The phosphate rock is selected from flotation phosphate rock of Batiandian in Guizhou Province, the chemical composition is shown in Table 1, ammonium sulfate (99.0%), hydrochloric acid (36%) and methanol (99.5%) are all analytically pure.

[0051] Table 1 Composition of Batiandian flotation phosphate rock

[0052] P2O5 CaO MgO Fe2O3 Al2O3 Si2O F 26.16% 43.26% 5.9% 0.33% 0.36% 4.38% 1.76%

[0053] 1.3 Experimental steps and process flow

[0054] First, high-temperature solid-state reaction is carried out. Phosphorite and ammonium sulfate are weighed by an analytical balance respectively, mixed uniformly according to a certain ratio, placed in an evaporating dish, heated by an electric heating jacket, and continuously stirred to ensure complete reaction.

[0055] Phosphoric acid is extracted by using methanol solvent. A sufficient amount of methanol solution is added to the fully reacted sample, fully stirred, and the generated phosphoric acid is extracted, and then filtered by using a vacuum pump filter to obtain phosphoric acid filtrate and residue.

[0056] The filtrate is distilled to obtain pure phosphoric acid. The filtrate is distilled by using a rotary evaporator at a temperature of 80°C and a rotation speed of 60 r / min to obtain pure phosphoric acid, which is weighed and stored. The phosphorus (P2O5) content in the product phosphoric acid solution is measured by using the phosphomolybdic acid quinoline gravimetric method, and then the phosphoric acid yield is calculated.

[0057] Finally, the unreacted ammonium sulfate in the residue is separated. The residue is dissolved in water, filtered by using a vacuum pump filter to obtain impurity residue such as calcium sulfate and ammonium sulfate solution, so that the ammonium sulfate is recycled.

[0058] The above experimental process is represented by a process flow chart as shown in Figure 1 : Process flow chart for preparing phosphoric acid by flotation of phosphorite.

[0059] 2. Experimental results and discussion

[0060] 2.1 Effect of reaction temperature on phosphoric acid yield

[0061] In the experiment of exploring the effect of temperature on the yield of phosphoric acid, the reaction time is fixed at 1 h, the mass ratio of ammonium sulfate to phosphorite is 1:1, and the PH value of the methanol extraction liquid reflects the phosphoric acid yield of the experiment.

[0062] 5 g of Baidian phosphorite and ammonium sulfate are weighed and placed in an evaporating dish (6 groups), stirred and mixed by using a medicine spoon, heated by using an electric heating jacket heating device (6 groups of temperature are set to 200°C, 250°C, 270°C, 300°C, 350°C, and 400°C), and high-temperature solid-state reaction is carried out for 1 h. After the reaction is completed, the phosphoric acid obtained after the reaction is extracted by using methanol solution. The six groups of experiments are carried out simultaneously to explore the effect of different temperatures on the yield of phosphoric acid. The decomposition degree of ammonium sulfate is judged by the reduction amount of the sample before and after calcination. The decomposition reaction product is extracted by using 100 g of methanol (extraction time 0.5 h), the extraction liquid is distilled for 0.5 h, the methanol vapor is removed, the pH of the final aqueous solution is detected, and the phosphoric acid yield of the experiment is judged. The experimental results are shown in Table 2, Figure 2 .

[0063] Table 2: Effect of reaction temperature on yield of phosphoric acid (weighing, solid-state reaction)

[0064] Group Evaporating dish mass / g Phosphate rock mass / g Ammonium sulfate mass / g Reaction temperature (℃) Reaction time / h Heating loss / g Raffinate mass / g Raffinate pH value 1 48.5 5 5 200 1 0.21 50.34 6.00 2 48.5 5 5 250 1 1.23 51.26 2.00 3 48.5 5 5 270 1 2.14 51.01 1.00 4 48.5 5 5 300 1 2.24 51.32 1.50 5 48.5 5 5 350 1 3.56 50.10 5.00 6 48.5 5 5 400 1 3.74 50.00 7.00

[0065] From Table 2, Figure 2 It can be seen that the pH value of the methanol extract first decreases and then increases with temperature, and the pH value of the methanol extract is the smallest at about 270°C, that is, the phosphoric acid yield is the highest. Therefore, it is concluded that the optimum temperature of the reaction is 270°C.

[0066] At 270°C, the ammonium sulfate in the reactant is completely decomposed to generate ammonium bisulfate, which is further decomposed into sulfuric acid and ammonia gas, and the phosphate rock reacts with sulfuric acid to obtain phosphoric acid product. Below 270°C, ammonium bisulfate does not reach the decomposition temperature, resulting in incomplete reaction. When the temperature is higher than 270°C, ammonium bisulfate is decomposed into ammonia gas, sulfur dioxide, nitrogen gas and water vapor at high temperature, which cannot react with phosphate rock.

[0067] 2.2 Effect of ammonium sulfate and phosphate rock ratio on phosphoric acid yield

[0068] In the experiment of exploring the influence of the ratio of ammonium sulfate to phosphate rock on the yield of phosphoric acid, the reaction temperature was fixed at 270°C and the reaction time was 1h. According to the ratio of ammonium sulfate to phosphate rock of (1:1), (1.5:1), (2:1), (3:1) and (6:1), the yield of phosphoric acid with different proportions was obtained.

[0069] 30g of ammonium sulfate was weighed and placed in an evaporating dish (5 groups), and the corresponding mass of Baidian phosphate rock was weighed according to different proportions and placed in the corresponding evaporating dish. The mixture was stirred and mixed with a medicine spoon, and heated using an electric heating jacket heating device for 1h high temperature solid state reaction. The phosphoric acid obtained after reaction was extracted with methanol solution, and the actual yield of phosphoric acid was determined by phosphomolybdic acid quinoline gravimetric method. Five groups of experiments were carried out simultaneously to explore the influence of different proportions on the yield of phosphoric acid. The results are shown in Tables 3, 4, Figure 3

[0070] Table 3: Influence of ratio of ammonium sulfate to phosphate rock on yield of phosphoric acid (P2O5) (weighing, solid state reaction)

[0071] Group Evaporating dish / g Phosphate rock / g Ammonium sulfate / g Ammonium sulfate and phosphate rock ratio Firing temperature (℃) Firing time / h Heating loss / g 1 82.04 30 30 1 270 1 6.83 2 82.04 20 30 1.5 270 1 6.88 3 82.04 15 30 2 270 1 6.74 4 82.04 10 30 3 270 1 6.03 5 82.04 5 30 6 270 1 4.12

[0072] Table 4: Influence of ratio of ammonium sulfate to phosphate rock on yield of phosphoric acid (P2O5) (extraction, determination of phosphoric acid yield)

[0073] Group Methanol / g Extraction time / h Filter residue drying time / h Filter residue mass / g Filter liquid mass / g P% Phosphoric acid actual yield / g Phosphoric acid theoretical yield / g Phosphoric acid yield / % 1 120 0.5 1 32.54 124.14 0.934 1.16 4.48 25.80 2 120 0.5 1 32.17 119.35 0.830 0.99 2.99 33.11 3 120 0.5 1 24.18 111.91 1.000 1.20 2.24 53.57 4 120 0.5 1 15.17 149.38 0.945 1.41 1.50 94.00 5 120 0.5 1 10.29 128.05 0.375 0.94 0.99 94.95

[0074] From Tables 3, 4, Figure 3 ​It can be seen that the mass ratio of phosphoric acid (P2O5) increases gradually with the decrease of the mass ratio of phosphate rock in the reaction, and the yield gradually tends to be flat when the mass ratio of sodium sulfate to phosphate rock is 3:1. Therefore, it is concluded that the reaction effect of ammonium sulfate and phosphate rock is best when the mass ratio of ammonium sulfate to phosphate rock is 3:1, and the yield of phosphoric acid (P2O5) is highest, which can reach 94%.

[0075] 2.3 Effect of reaction time on phosphoric acid yield

[0076] In the experiment of exploring the effect of time on the yield of phosphoric acid, the reaction temperature is fixed at 270°C, the mass ratio of ammonium sulfate to phosphate rock is 3:1, and the mass reduction of the reactants in different time periods reflects the phosphoric acid yield of the experiment.

[0077] Take 10g of Baidian phosphate rock and 30g of ammonium sulfate and place them in an evaporating dish, mix them evenly with a spoon, and use an electric heating jacket heating device for high-temperature solid-state reaction. During the reaction process, record the mass reduction of the reactants at different times to determine the decomposition degree of ammonium sulfate before and after the reaction, and use it to determine the phosphoric acid yield of the reaction. The experimental results are shown in Table 5, Figure 4 .

[0078] Table 5: Effect of reaction time on phosphoric acid yield

[0079] Group Evaporating dish / g Phosphate rock mass / g Ammonium sulfate mass / g Temperature / ℃ Time / min Decrease before and after calcination / g 1 82.02 10 30 270 0 0 2 82.02 10 30 270 10 2.8 3 82.02 10 30 270 20 1.93 4 82.02 10 30 270 30 1.55 5 82.02 10 30 270 40 0.12 6 82.02 10 30 270 50 0.05 7 82.02 10 30 270 60 0.02

[0080] As shown in Table 5, Figure 4 , in the process of high-temperature solid-state reaction, with the increase of time, ammonium sulfate begins to decompose, ammonia gas is generated, and the total mass of the reaction process begins to decrease, and the decrease amount decreases with time. When the reaction time reaches 40min, the total mass of the reaction process decreases by only 0.12g during 30-40min, indicating that ammonium sulfate has been completely decomposed at 30min. Therefore, it is concluded that the best reaction time of the reaction is 30min. In this time, ammonium sulfate is completely decomposed and the reaction energy consumption is lowest.

[0081] 3. Conclusion

[0082] 3.1 This experiment controls the variables, explores the reaction temperature, the ratio of reactants ammonium sulfate and phosphate rock, and the reaction temperature, and concludes that when the reaction temperature is 270°C, the ratio of reactants ammonium sulfate and phosphate rock is 3:1, and the reaction time is 30min, the yield of phosphoric acid is highest and the experimental effect is best. 3.2 This experiment realizes the utilization of medium and low grade phosphate rock by high-temperature solid-state calcination method, the process is simple and easy to operate, and the calcination temperature is relatively low, the energy consumption is low.

Claims

1. A method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate, characterized in that: The method for preparing phosphoric acid is to use phosphorite and ammonium sulfate as raw materials, and to prepare pure phosphoric acid by high-temperature solid-state reaction; The method has the following specific steps: (1) phosphorite and ammonium sulfate are weighed respectively, the mass ratio of phosphorite to ammonium sulfate is 1:3-6, and the phosphorite and ammonium sulfate are placed in an evaporating dish and heated at a high temperature of 250-300 DEG C for 30-40 min by using an electric heating jacket, the stirring is continuously performed during the heating process, and after the reaction is completed and cooled, a crude phosphoric acid is obtained; (2) the crude phosphoric acid is taken and extracted by 100-150 g of methanol for 10-60 min, the extraction process is fully stirred, and a vacuum pump filter is used for filtration, so that a phosphoric acid filtrate and a filter residue are obtained; (3) the phosphoric acid filtrate is taken and distilled by using a rotary evaporator, the distillation temperature is 60-100 DEG C, the rotating speed is 50-70 r / min, and the distillation time is 30-100 min, so that pure phosphoric acid is obtained; (4) the filter residue is dissolved by adding water, a vacuum pump filter is used for filtration, the filtrate is taken, and the impurity filter residue is removed, the filtrate is an ammonium sulfate solution, and can be used for the cyclic preparation of phosphoric acid.

2. The method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate according to claim 1, characterized in that: In the step (1), the high-temperature heating reaction temperature is 270 DEG C, and the reaction time is 30 min.

3. The method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate according to claim 1, characterized in that: In the step (2), the addition amount of the methanol is 120 g, and the extraction time is 20-60 min.

4. The method for preparing phosphoric acid by high-temperature solid-state reaction of phosphate rock and ammonium sulfate according to claim 1, characterized in that: In the step (3), the distillation temperature is 80 DEG C, the rotating speed is 60 r / min, and the distillation time is 40-90 min.

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